This is the concept used in a trompe. Basically, the idea is that if we allow water to flow down a pipe and if that pipe has inclined air intake orifices near the top where the water enters, then the water will entrain air bubbles down into a reservoir where the air bubbles can then escape the downward pressure of water releasing compressed air in the reservoir while the water escapes through an exit pipe. I would like to know how water is capturing air when it is pulled by gravity down a tube and what variables determine how much air will be captured. Here is a video describing the overall concept if interested: Trompe Concept Video.
